This invention relates to mounting devices, and, more particularly, to an improved mounting assembly for securing objects to vertical supports such as a wall.
Expansible sleeves or anchors are used in a variety of applications to secure an object in place on a given surface. Expansible anchors generally include a sleeve, often formed with threads or projections along its outer surface, which is adapted to be inserted within a bore formed in the surface to which an object is to be mounted. An axial bore is formed in the sleeve which is adapted to receive a pin of greater diameter so that when the pin is inserted into the bore the walls of the sleeve are urged apart or expanded to wedge the sleeve into position within the bore formed in the mounting surface.
One limitation of such prior art expansible anchors is that a hole must first be drilled in the mounting surface to receive the sleeve. This increases the difficulty in mounting objects to relatively soft, easily breakable surfaces such as the plaster or plaster board walls of a building. If the hole in the plasterboard is made too large, the sleeve may become loosened or pulled out of the wall under the application of downward loading.
To avoid the step of first boring a hole in a surface such as plaster or plaster board, self-drilling anchor shields or sleeves have been developed such as disclosed, for example, in U.S. Pat. No. 4,050,344. Anchor sleeves of this general type comprise a hollow nail-like plug or sleeve having a body formed with a point at one end and a striking surface or head section at the other end. An axial bore is formed part way along the body, and radial slots extend along the body to separate it into two or more body portions. To secure the anchor sleeve to a mounting surface, the pointed end of the sleeve is first driven into the mounting surface by striking the head section of the sleeve with a tool such as a hammer. A pin is then inserted through the axial bore and between the body portions to urge them apart and into engagement with the mounting surface.
While anchors of this type avoid the separate operation of first forming a bore in the mounting surface, their effectiveness in supporting the weight of a heavy object on a breakable surface such as plaster or plaster board is limited by at least two factors. First, expansion of the body portions of the sleeve within the mounting surface is limited to the diameter of the pin inserted within the sleeve. As the pin is inserted between the body portions of the sleeve the body portions are urged apart, but no further apart than the outside diameter of the pin. In addition, there is no assurance that prior art anchor sleeves will be oriented within the mounting surface so that the body portions expand in the same direction as the vertical force tending to pull the sleeve out of the wall or other surface. It can be appreciated that the load carrying capability of any anchor sleeve is maximized when the body portions of the sleeve or plug are expanded in a vertical direction within the mounting surface, or parallel to the direction in which the load is applied to the sleeve. The load tends to urge the body portions directly into the mounting surface, instead of outwardly from the mounting surface as could occur if the body portions were expanded along an axis disposed at an angle to the axis of the applied load. In prior art anchor sleeves, proper positioning of the plug is entirely dependent on the skill of the individual installing it and there is no fail-safe feature to assure that the body portions of the sleeve are oriented parallel to the vertical axis in which the load is applied by an object to be mounted.